Wetproof cigarette paper



Patented May 9, 1944 WETPROOF CIGARETTE PAPER Allen M. Bond, Jr'., Louisville,-Ky., assignor to Brown & Williamson Tobacco Corporation, Louisville, Ky., a corporation of Delaware No Drawing. Application May 21, 1941, Serial No. 394,482

4 Claims.

This invention relates to the manufacture of cigarette paper rendered wet-proof or water resistant, and relates particularly to an in proved wet-proof cigarette paper.

Several proposals have heretofore been made for manufacturing water-repellent cigarette paper or for treating cigarette paper to render the same water-proof,.and while. some of these proposals have proved generally satisfactory, they are attendant with certain objections either because of the difficulties involved in manufacturing or treating the cigarette paper or because of some one or more disadvantages in the use of the ultimate product.

In order for cigarette paper to have the requisite qualities to produce a cigarette of sat' isfactory burning characteristics, the paper must be both thin and porous. Such a paper tends, by the very nature of its structure, to be absorbent and, on becoming wet with moisture, to disintegrate. It is this tendency which causes unprocessed cigarette paper either to disintegrate or to stick to the smokers lips. Paper impregnated with the water-repellent compound of the present invention is sufficiently water-resistant to make it impossible for a cigarette made therefrom either to disintegrate under. the action of saliva or to adhere to the smokers lips with such a tenacity as to cause a tearing of the paper, the lip-skin, or both.

Due to the adverse action of wateron untreated paper, most smokers find it unsatisfactory to smoke cigarettes either in the rain or while their hands are wet. Cigarettes made with the paper of the present invention may be smoked with normal satisfaction even under these abnormal conditions.

to use water soluble paste. Under atmospheric conditions of excessive humidity, it is possible for the adhesive seam to become so weakened by moisture as to permit the cigarette to burst 'open.

with, particularly in the character of the ultimate cigarette paper product. These requirements which are very effectively satisfied by the water-repellent compound of my present invention, are in addition to (1) maximum water-repellency as follows: -(2) complete nontoxicity,

In making the adhesive seam of cigarettes, it is common practice (3) minimum effect on the opacity of the paper, (4) minimum effect on the porosity of the paper, and (5) the ability of being applied by simple commercial processes.

It is further of importance to be able to meet these conditions and accomplish all of the desired results with the use of a very small amount of the water-repelling agent or compound.

I have found that aluminum stearate, a water insoluble metal salt derived from stearicacid, possesses these especial advantages as a wetproofing medium for cigarette paper. I have found that aluminum stearate may be deposited on the cigarette paper in relatively small amounts for accomplishing all the desired ends, the required deposits being as little as 0.05 to 0.2 pound per one thousand square feet of the cigarette paper, such an amount effecting an increase ln the paper weight of as little as 1% to 5%. This water insoluble metal salt of stearic, acid possesses the stated and other advantages in a very high degree.

Complete non-toxicity.To produce complete nontoxicity, the wet-proofing medium should not add a foreign flavor or aroma and should have a minimum decomposition or combustion at the burning or smoking temperature of the cigarette paper. The most serious hazard of any treatment designed to wet-proof cigarette paper is that of introducing a foreign taste or odor to the cigarettes made therewith. For the purpose of rendering cigarette paper water-resistant, the use of resinous films, cellulose derivative films, wax-like sheaths, and coatings formulated with mineral oils have been suggested. In the case of most of these treatments, 8. foreign flavor or aroma is quite evident. In all of them of which I am aware, there is introduced to the cigarette some material which undergoes limited combustion, giving off combustion products different from those produced by the burning of tobacco and untreated cigarette paper. I have found that the water-repellent medium of the present invention does not impart any foreign flavor or aroma. Because this wet-proofing material is insoluble in water, it cannot be dissolved from the paper itself by the saliva of the smokers lips and thus no foreign taste can come from the paper through contact with the smokers mouth. I have found no evidence that this material undergoes combustion at the temperature to which the paper in a burning cigarette is subjected.

Minimum effect on the opacity of the pape1t- The effect of impregnating any paper with wax and/or oil is a tendency towards translucence. In the case of cigarette paper, this is equivalent to a loss of opacity. This represents a serious disadvantage; the property of opacity is carnestly sought by the cigarette paper manufacturer. I am aware that it has been proposed to precipitate stearic acid in the cigarette paper pulp so that this material forms a wet-proofing ingredient in the paper product. In addition to the difiiculties involved in manufacture and other drawbacks incident thereto, stearic acid unless used in large amounts, which in itself involves a disadvantage, tends to effect a loss of opacity in the cigarette paper. The aluminum stearate compound of the present invention not only possesses a maximum whiteness in solid state, but

forms a water-repellent medium on the paper which, instead of decreasing the opaque quality or opacity of the paper, actually enhances or increases the same.

Minimum efiect on the porosity of the paper.- The burning rate of a cigarette paper is related to the porosity of the cigarette paper of which it is made. Generally speaking and assuming that all other factors affecting the burning rate of cigarettes are kept constant, the lower the porosity the lower the rate of burning. For this reason cigarette manufacturers specify a given porosity fo the cigarette paper which they purchase, and cigarette paper manufacturers accordingly control the porosity of their products throughout a wide range of specifications. It is highly important that the deposited water-repellent medium be discontinuous in character and so incorporated in the paper as to minimze the change in the porosity. I have found that as little as .08 pound of dry aluminum stearate per 1000 square feet of cigarette paper, sufficient to produce the abovementioned requisite properties, will not materially decrease the porosity of the paper. The porosity, for the range herein described, may be decreased by about 30%; and to compensate for this the cigarette paper used may be correspondingly more porous so that there is ultimately obtained a wet-proof paper of the same porosity as the regular unprocessed paper.

The ability of being applied by simple commercial processes.-The water-repellent medium should be capable of being coated on or impregnated with the paper by standard methods and at commercial speeds. I have found that aluminum stearate fully answers this requirement. The already manufactured paper may be readily coated or impregnated by immersion, spraying, or roller coating in a gelof aluminum stearate and an aromatic hydrocarbon solvent such as benzol, toluol and xylol. The cigarette paper may be fed through the coating machine and this gel applied at commercial speeds of from 200 to 300 feet of paper (35 inches width) per minute. In the process, after the desired coating is applied, the or.- ganic solvent is completely removed by evaporation as the paper is passed through the drier, leaving the thin deposit of dry aluminum stearate on the paper (preferably on both sides thereof).

The solvent used in this process should be one in which the stearate forms at practical temperatures a jelly which does not separate outat room temperatures. The aluminum stearate and such hydrocarbon slovents as benzol, toluol and xylol of the present invention are highly suitable for the wet-proofing of cigarette paper because the stearate is capable of dissolving in these solvents and at the same time forming at practica'ble temperatures jellies which do not separate out at normal room temperatures. The fact that these solvents are readily recoverable offers another advantage to their use. Due tothe fact that recovery of a single solvent is much simpler than recovery of a mixture of solvents it should be pointed out that any one of the above solvents may be used alone as the vehicle for the aluminum stearate. Finally, the technical grade of these solvents is suificiently free of high-boiling impurities that every trace of the vehicle may be evaporated, leaving no residual traces thereof in the treated paper.

In order to obtain thorough solution, proper jelling, good adhesion between aluminum stearate and paper, and uniform wet-proofing, I- have found it advisable to carry out a procedure such as the following, which may be stated as a preferred example: Powdered aluminum stearate is dissolved in the solvent such as toluol. As the temperature of the solution is slowly raised to 47-51 0., the same is gently agitated. Agitation is continued until all evidence of any tendency towards the separation of gels is removed. The solution is then permitted to cool to room temperature and is ready for the coating or impregnating step.

As anexample of the strength of solution, I may cite an 0.5% to 4% solution of aluminum stearate in xylol. I have found that a 1.5% solution of aluminum stearate in toluol yields very desirable results; the deposit on the paper with this example being about 0.08 pound of the dry aluminum stearate per- 1000 square feet of paper, yielding an increase in weight of the paper of the order of about 2%. A. preferred range may be considered as 0.5% to 1.5% solution strength; and working within this range I am able to apply .05 to .2 pound of solids per 1000 square feet of paper. These examples give thorough solution, proper gelling, good adhesion between the aluminum stearate and paper, and uniform Wetproofing,

I have also found that for the best results an alumnum stearate should be used which has a minimum amount of -free fatty acid. As an example of the aluminum stearates I prefer to employ are four aluminum stearates produced by Harshaw Chemical Company of Cleveland, Ohio; these are identified by the manufacturer as #40 having 4.90% free fatty acid, #26 having 9.90% free fatty acid, #27 having 14.60% free fatty acid, and Technical A-30 having 16.90% free fatty acid. With these materials from .10 to .15 pound per thousand square feet of paper yield satisfactory wet-proofing. With the #40 aluminum stearate, no foreign flavor is introduced with asmuch as .30 pound of deposited material. To avoid the introduction of even a suspicion or trace of foreign flavor, I recommend the material having the minimum free fatty acid.

In addition to the properties above referred to, I have found that with the cigarette paper of the present invention, spotting or staining of the paper is lessened. Under certain conditions, tobacco in the manufactured form of cigarettes undergoes a phenomenon known as sweating. This is abetted by manufacturing cigarettes from out tobacco of excessive moisture content. This sweating results in a spotting, staining, and/or discoloration of the cigarette paper, and this is due to the absorption by the paper of certain water soluble organic compounds present in the tobacco. By experimental evidence, I have demonstrated that the cigarette paper of the present invention is far more resistant to such spotting, staining and/or discoloration than is untreated cigarette paper. Spotting of cigarette paper also results when cigarettes are made from tobacco into which such casing materials as glycerine, invert sugar, etc. have not sufliciently penetrated. The cigarette paper of the present invention is far more resistant to such unabsorbed casing" than is unprocessed paper.

The manufacture of Wet-proof cigarette paper embodying the principles of the present invention and the advantages thereof will in the main be fully apparent from the above detailed description thereof. It will be further apparent that changes may be made from the examples given of the preferred manner of practicing the inven- I claim:

1. A wet-proof cigarette paper consisting of cigarette paper coated with aluminum stearate in an amount of the order of 0.05 to 0.2 pound of dry aluminum stearate per one thousand square feet of cigarette paper.

2: A wet-proof cigarette paper consisting of cigarette paper coated on both sides with aluminum stearate, the aluminum stearate being of the order of 1% to 5% by weight of the cigarette paper.

3. The wet-proof cigarette paper of claim 1 in which the aluminum stearate has a minimum of free fatty acid.

4. The wet-proof cigarette paper of claim 1 in which the aluminum stearate contains not more than 5% of free fatty acid.

ALLEN M. BOND, JR. 

